. Multi-generational studies provide conclusive evidence for the transmission of smoking behavior from parent to child. The proposed study will test a strategy for preventing intergenerational transmission of smoking. An evidence-based parenting program for child smoking prevention will be disseminated to parents who smoke as they initiate use of evidence-based telephone (Quitline) smoking cessation services. A two-group, randomized controlled trial will test the effects of combining the evidence-based parenting program for child smoking prevention, called Smoke-free Kids, with the evidence-based adult smoking cessation services of state Quitlines. Smoke-free Kids is a home-based, self-directed program that engages parents who smoke in anti-smoking socialization of children. All of the anti-smoking socialization activities recommended by this program are equally relevant to parents who are making a quit attempt. The trial will examine program effects on child initiation of smoking and on parent maintenance of smoking cessation. Summary. Eligible children will be eldest male or female children from single- or two-parent households, of any race/ethnicity, who will be ages 7 to 9 at baseline, in the pre-initiation stage of smoking, and enrolled with a parent, stepparent, or other guardian who lives with the child and who has begun using Quitline cessation services. In partnership with state Quitlines, rolling recruitment will be used to enroll 1,294 eligible children and their parents. Participants will be assigned randomly within states to either the treatment (adult cessation services plus child smoking prevention program), or control (adult cessation services only) group. Participants will follow a 36-month protocol between random assignment and final follow-up. Parents will complete baseline assessments plus follow-up interviews 1 and 6 months post-intervention and annually thereafter; in addition, treatment group parents will complete program implementation surveys. Children will complete baseline assessments plus follow-up interviews 1 and 6 months post-intervention and annually thereafter; they will be ages 10 to 12 at final follow-up. The study hypotheses posit reduced odds of child initiation of smoking (first instance of puffing on a cigarette), lower child susceptibility to smoking, and increased likelihood that parents will maintain smoking cessation. Survival analysis will test the effects of the intervention on initiation of smoking among children and on maintenance of cessation among parents. A proportional odds model will test the effects of the intervention on susceptibility to smoking among children who do not initiate smoking. Regression analyses and latent variable modeling will be used to identify mediators and moderators of intervention effects. Cost-effectiveness analyses will also be conducted.